Derivative Financial Instruments (Details 3) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Amounts presented in consolidated balance sheets(1)
Gross and net amounts presented in consolidated balance sheets, Total derivative assets	$ 0.5	[1]	$ 74.3	[1]
Gross and net amounts presented in consolidated balance sheets, Total derivative liabilities	48.4	[1]	0	[1]
Gross and net amounts presented in consolidated balance sheets, Net assets	(47.9)	[1]	74.3	[1]
Gross amounts not offset in consolidated balance sheets
Financial instruments, Total derivative assets	0.5		0.2
Financial instruments, Total derivative liabilities	0.5		0
Financial instruments, Net assets (liabilities)	0		0.2
Net Amount, Total derivative assets	0		74.1
Net Amount, Total derivative liabilities	47.9		0
Derivative asset (liability), net	$ (47.9)		$ 74.1

[1] We report the fair values of our derivative assets and liabilities on a gross basis on our consolidated balance sheets. As a result, the gross amounts recognized and net amounts presented are the same.